RECORD-BREAKING APRIL MUCH WARMER, MUCH SUNNIER, AND WETTER THAN AVERAGE
Armagh Observatory, 10th May 2025: Armagh Observatory reports that April 2025 was a record-breaking month, much warmer, much sunnier, and wetter than average. It was the third warmest April on record at Armagh, the third sunniest, and the wettest at Armagh for seven years.
Despite higher-than-average precipitation, the month was mostly dry with just seven rain days, that is, days with precipitation greater than or equal to 0.2 mm, and more than three-quarters of the month’s total precipitation fell during just three days. The mean temperature was 10.75 degrees Celsius, approximately 2.8 C warmer than the 225-year long-term (1796-2020) April average at Armagh (7.92 C), and nearly 2.0 C warmer than the most recent (1991-2020) 30-year average (8.80 C). This was the warmest April at Armagh for 14 years, that is, since the exceptionally warm April 2011 (11.75 C). The five warmest Aprils at Armagh are now April 2011 (11.75 C), April 2007 (11.25 C), April 2025 (10.75 C), April 2014 (10.48 C), and April 2020 (10.20), tied with April 1944.
Daily maximum temperatures were also relatively high, in part owing to the month’s unusual amount of strong sunshine. The mean of the daily temperature maxima (16.0 C) was the third highest such average on record and the highest for 14 years, that is, since the record-breaking April 2011 (16.6 C). This year’s figure was approximately 3.0 C greater than the most recent (1991-2020) 30-year such average for April at Armagh (13.0 C). The three years with highest average maximum temperatures during April at Armagh are now 2011 (16.6 C), 2007 (16.4 C), and 2025 (16.0 C).
Conversely, the average of the daily temperature minima, approximately 5.5 C, was only 0.8 C warmer than the most recent (1991-2020) 30-year average (approximately 4.6 C) and the 15th warmest such average on record at Armagh. This illustrates the effect of relatively clear skies at this time of year: much higher-than-average daytime temperatures but relatively cool nights.
The highest maximum air temperature, that is, the warmest day, was 23.4 C on the 30th, followed by 21.8 C on the 10th and 21.7 C on the 11th. The 30th was the warmest April day on record at Armagh, that is, in a daily temperature series beginning in December 1794. It was also the warmest day of the year up to the end of April and probably early to mid-May as well.
The exceptionally warm 30th April surpassed the previous record, namely 22.6 C on both 25 April 1975 and 26 April 1987, by 0.8 C. The following fourth and fifth warmest April days at Armagh are now 27 April 1987 (22.4 C) and 20 April 2019 (22.3 C).
The second and third warmest days this April, that is, the 10th and 11th of April 2025, are also the two warmest days on record at Armagh during the first half of April. The five warmest days at Armagh during the first 15 days of April are now the 10th and 11th of April 2025 (21.8 C and 21.7 C respectively), followed by 3 April 1946 (21.0 C), 14 April 2007 (20.9 C), and 2 April 1946 (20.6 C).
The lowest maximum air temperature or coolest day, was 8.6 C on the16th, followed by 9.2 C on the morning of the 19th but attributed by convention to the 18th, and then by 10.4 C on the 19th. These cool days were associated with a period of unsettled weather beginning on the 12th of April and which, on the 16th and 22nd, provided the most significant rainfall of the month.
The highest minimum air temperature, usually the warmest night, was a mild 11.5 C on the 28th, followed by 11.2 C on the 27th and 10.4 C attributed to the 26th. The 28th was the eighth warmest April night on record at Armagh, shared with 19 April 2018.
The lowest minimum air temperature, usually the coldest night, was -0.2 C on the 7th, followed by 0.4 C on the 8th, and 1.6 C on the 17th.
There were several quite sharp ground frosts among the 17 nights with recorded grass minimum temperatures less than or equal to zero Celsius of which the lowest three were -6.9 C on the 8th, -6.5 C on the 7th, and -5.4 C on the 6th. There was only one day, namely the 7th, with a nighttime air frost.
There were no named storms this month and few April showers. Instead, the month was dominated by high atmospheric pressure. The mean 09:00 GMT atmospheric pressure reduced to mean sea level was approximately 1018 mbar, almost 4 mbar higher than the corresponding most recent (1991-2020) 30-year average (1014 mbar). This was the highest average April atmospheric pressure for four years, that is, since April 2021 (mean pressure reduced to mean sea level of 1026 mbar).
A buzzard was noted circling over nesting rooks on the morning of the 1st, and a rainbow was observed on the afternoon of the 13th followed on the 14th by a brief but heavy hail shower. Total precipitation this April was 64.8 mm with no trace values. Despite the relatively large number of dry days (16 days with no precipitation), this was wetter than average with approximately 23% more rainfall than the 183-year long-term (1838-2020) average at Armagh (52.75 mm) and 16% more than the most recent (1991-2020) 30-year average (55.89 mm). It was also the wettest April at Armagh for seven years, that is, since April 2018 (total precipitation 75.85 mm including five trace values).
The wettest meteorological day, which begins at 09:00 GMT, was notionally the 22nd with 14.5 mm of precipitation, followed by the 18th (Good Friday 2025) with 14.3 mm, and the 16th with 10.7 mm. However, persistent heavy rain began on the 16th at around 03:10 GMT and continued all day until approximately 18:40 GMT, supplying a total accumulation of 20.7 mm during the day. The reason this did not count as the wettest day of the month was that, following standard meteorological procedures, this total amount was split across two meteorological days: 10.2 mm before 09:00 GMT on the 16th (and so attributed to the 15th) and 10.7 mm after 09:00 GMT (and attributed to the 16th).
This April was also very sunny with 212.0 hours of strong sunshine, a value approximately 46% more than the 140-year (1881-2020) long-term April average at Armagh (145.54 hours) and 41% more than the most recent (1991-2020) 30-year average (149.87 hours). April 2025 was therefore much sunnier than average, the third sunniest April on record at Armagh and the sunniest for five years, that is, since April 2020 (213.7 hours of strong sunshine). The four sunniest Aprils at Armagh are now April 1902 (221.6 hours), April 2020 (213.7 hours), April 2025 (212.0 hours), and April 2021 (210.5 hours).
With the exception of the 4th, which nevertheless had a respectable 4.6 hours of strong sunshine, the first 11 days of the month were all exceptionally sunny for early April. Taken together they produced an average of 10.6 hours of strong sunshine per day. The occurrence of such a long sunny spell in the first half of April is unprecedented in the Observatory’s daily sunshine record, which began towards the end of April 1880, though a comparable sunny spell occurred from the 21st to the 30th of April 1918. The sunniest day this April 2025 was the 23rd, with 12.8 hours of strong sunshine, followed by the 5th, 7th, and 8th, which each had 11.6 hours.
These data refer to observations at Armagh Observatory, which has been recording the weather at Armagh since 1795.
For further information, please contact:
Professor Mark E. Bailey
Emeritus Director of Armagh Observatory
Armagh Observatory and Planetarium
College Hill
Armagh
BT61 9DG
Tel: 028-3752-2928
E-mail: mark.bailey@armagh.ac.uk